Drawing board



March 1 5, 1932. L N 1,849,493

DRAWING BOARD Filed Feb. 16. 1928 2x .3619): A3 [Jar/rip INVENTOR ATTORNEY Patented Mar. 15, 1932 PAT DENNIS F. LARKIN, or SAN FRANCISCO, CALIFORNIA.

DRAWING BOARD Application filed February 16, 1928. Serial masa'zaa This invention relates to improvements in drafting apparatus and more particularly to a combined drawing board, paper holder, straight edge graduated T square, etc.

Among the objects of the inventionare to provide a simplified combination of the instruments above enumerated so constructed combined and arranged that the straight edge of guide member will also act as a paper clamp for holding the drawing paper on the drawing board. The guide member and the T square are of such constructionand arrangement thatthe angular straight edge will guide the T square in laying ofi'lines horizontal to the straight edge; and also so formed and arranged that the T square may be used as a lever in prying open the paper holding clamp in inserting or removing the drawingpaper from the drawing board. Other objects and advantages will appear as this description progresses. v

In this specification and the accompanying'one sheet of drawings, the invention is shown in the form considered the best but I do not wish to be understood as confining it to this form because it may be embodied in other forn1s, and it is also to be understood that in and by the claims following the-de scription it is desired to cover the invention'in 0 whatsoever form it may be embodied.

In the drawings, Fig. 1 is an isometrical perspective from above ofa' drafting apparatus constructed in accordance with this in vention, parts of the drawing board being omitted for obvious reasons. Fig. 2 'is an enlarged detail in side elevation, illustrating the combination andfarrangement of the various parts of the structure, the dottedlines showing the double use of the square when 0 usedas a pry for opening the paper clamp.

Fig. 3 is atransverse section of the blade of theT square. Fig. 4-, is a simplified modification of the invention in Whic'h'the lower j awof the clamp serves as the drawing board.

5 In detail the construction illustrated in the drawingscomprises, ajdrawing board of any desired dimension, although the invention is illustrated primarily for 'small portable drafting outfits. Heavy'chip board or light veneer board is very suitable for the drawing .with the paper,12 held beneath the clamp 5.

board 1. The combined straight edge guide is pre clamp under jaw lyingbeneaththe lateral edge of the drawing board 1, around which paper holder anderably formedof 'a single strip 1 of a sheet metal 2 to form the 5 it is bent upwardly andrearwardly' to'form the plane 6, preferably at arrangle of'about 45 degrees. It is again=bentat 7 torform the downwardly extended diverging plane 8,

at an angle of about 30 degrees-from the plane 6, vAtintervals the attaching lugs 9,

are cut from the bodyf ofjthe plate2 and curled inward thereover' as [at 10, and-are crimped' on to the lateral margin of the drawing'board to securely attach the plate 2 theroto. 'To insure the permanence of this attachment, the inner ends of these lugs .9 may be flanged downwardly as at 11 and forced into the body of the board 1; Punchin out these lugs 9 at intervals has the double a vantage of providing the lugs 9for attaching, the clamp to the board 1 and also weakens the tensilestrength'ofthe, curled portion 3, mak-- ing it more easy to open the clip for the insertion orremovalof the drawing. paper 12,

resting upon the table 1 and held in position by the spring. action of the clamp where its bentportion 5 bears upon the topmost sheet The diverging angles of the plates 6' and 8, being parallel with the lateral edge of the :drawing board l, forms a straight edge or guide for the T square. The T squarehas a head formed of the plates 13 and l l'bent at .the-sameangles and adapted to fit snugly over 7 V and slidablyengage the plates 6 and 8, the

plane'14 extending downwardly to' contact The angular head of the'T square 'has. an.

the width of the blade 15, the'lower extension of thehead presenting the edge 16, 90- degrees ';to' the edge 15 of the blade and parallel withthe said' straightedge. I 1 1 p v V For; convenience in handlingtheT squareabove the jaw 4, so that the plane '14 of the head of the T square lies against the bend 3 of the paper holder, see dotted lines Fig. '2.

When in this position downward pressure on the blade 15 of the T square, using the bent portion 53 :asafulcru-m, tends to pry open the clamp to lift the edge 5 from the surface of the paper .12, so that paper sheets may be very easily inserted or removed from between the top of the drawing board 1 and the clamping edge By thus utilizing the leverage of the '1' square as described, it is possible to make use of a QJIOn-gl spring tension in the curled edge 3 to accomplish a stronger clamping action again% the paper 12 at 5.. v

For convenience in laying off any draftingon the paper 12,.the length of the T square blade is graduated from the left from zero in inches throughout the length of the blade, with each inch further .graduatedinto equal dimensions as is common to measuring rules. As :a finther convenience these numerical divisions are reversed on the lower edge 19 of the blade, extending from zero at the right 'to the last dimension terminating at the edge .16. A further convenience is combined with the blade of the Tsquane by lay urg off :asca'le beginning, t zero in the-center of the Tsquare and extending numerically from one to the last dimension on both sides of the center from the edge 16 to the end of the T square blade. Obviously any system of graduation of inches, meters or the like may be scaled on the T :square.

The plane .6 of'the straight edge is also divided into inches or any other desired gradilation, for convenience in .spacing lines horizontal to the straight edge. Smaller giaduat'ions than those :onthe plane -16 may be placed along the edge -1 6,for .very fine measurements. The sheet metal parts forinthe combined straight edge .and paper clamp and T square are blanked .out'and formed from sheet metal between forming dies in the usual manner..-

Straddling the angular head of the T square down on the angular. plates- 6 and .8

of the guide tends to hold the T square in very rigid relation to the straight edge by a veryislig ht downward measure on the handle F117 This form of guide is much more dependlableithan the usual form of Tsquare .in which the head of the square bears against the edge 7 of the drawing board. Such :an engagement wouldbe unreliable :in an apparatus of this 'ing the T character where the light weight of the T square would tend to cause it to be veryeasily displaced, unless a very firm pressure to the right is constantly maintained on the head of the T square. By the present angular engagement of the head of the T square with the guide, greater lateral stability and accuracy can be maintained with a very short head on the T square. A further advantage is that the head of the'T square extends entirely above the plane of the blade 15 so that it can be used as a straight edge in drawing lines at any desired angle across the plane of the drawing paper, by merely lifting the head of the T square off the guide. The head of the T square in no way interferes with such use of the blade 15,-as would be the case if the plane 13 of the head extended below'the plane of the blade 15. When the T square is used independentlyof the guide, the angle between the edges 16 and 1 9 is also useful in determin :ing 90 degree angles in drafting operations.

In cutting sheet metal in dies as in formsquare, the edges cut by even the most accurate and sharp dies, leave the sheared edge of the T square rough along the edges .15 and 19. It is -desirable,therefore, to flange these edges downward as suggested in Fig. 3, thus presenting a smooth plane along the edges 15 and 19 against which the pencil of the 'draftsman may be guided without wearing away the pencil and-causing :a deposit of graphite dust on the surf-ace of the drawing paper, with obvious disadvan- ,tages.

A light, compact, simple and cheaply produced drawing apparatus such as shown an described ,isparticularly applicable to the demands of school students, surveyors, field -engineers, tool makers,. and similar voca tions' requiring small portable accurate apparatus. The guide being independent of the lateral edge of the drawing board 1, precision between the straight edge and the T square is alwaysmaintained. If a central line is drawn-along the'edge 5 before the drafting operation is started it is always possible then to remove and restore the work sheet under this edge 5 as often as desired,

accuracy being maintained "by al'ining this pencil line with the edge 5 each time the sheet is restored thereunder.

To avoid the necessity of using angles against the edge 15 of the T square, a second straight edge clamp may be clamped on. any of the other edges ofjthe drawing board at 90, or any desired angle to the first described straight edge guide. v In this "instance the lugs 9 need not-be countersunk into the surface of the drawing board, if itis desired toremove this second-clamp.

' The-designation T square is used for identification of this well known instrument, as a matter of fact it need not 'be a T shape but may be any desired modification, such as an L head as shown.

Although not so attractive in appearance, the guide clamp and T square head may be modified as shown in Fi 4. In this modification the angle of the gulde is reversed. The planes 6w8a2 are reversed so that the angular head 13w14a: of the T square rests within the guide. The mode of operation is substantially the same, but the structure can be .to overhang the edge of a board; lugs struck from the body of said material and adapted to be fixed to said board, an angular longitudinal guide formed in said clamp above said board and a T square having a head formed to slidably engage said guide.

2. A drafting apparatus comprising a strip of sheet metal bent back upon itself to form a resilient clamp, an angular guide formed by bending back one'edge of said clamp then flanging it downward; and a T square having an angular head adapted to slidably engage said guide and having an outward extension formed on said head and adapted to be inserted under said guide to open said clamp.

3. A drafting apparatus comprising a strip of sheet metal bent back upon itself longitudinally to form a resilient clamp, one

of the jaws of said clamp adapted to extend under a drafting board and the other jaw being bent back to form an angular guide above said clamp; and a T square having an angulardhead adapted to slidably engage said gui e.

4. A drawing board comprising a sheet metal plate having one of its edges bent over to form a resilient clamp to hold paper on said plate, a V shaped guide formed on the end of said bent over portion, the point thereof adapted to clamp the paper on said board,

and a T square having a V shaped head adapted to slidably engage and fit said guide and said paper.

5. A drafting apparatus comprising a strip of sheet metal bent back upon itself longitudinally to form a resilient clamp having an angular guide integral therewith, and a T-square having an angular head adapted to rest on and fit said guide.

6. A drafting apparatus in combination with a drafting board, a strip of sheet metal underlying said board and bent around the edge thereof to form a resilient clamp, the

upper jaw of said clamp being formed into an angular guide above the plane of said board, and a T squarehaving a raised angular head adapted to slidably fit said guide.

7. A drafting apparatus comprlsing a strip of sheet metal bent back upon itself longitudinally to form a resilient clamp, one of the jaws of said clamp being formed into an angular guide inclined from the perpendicular, and a T square having an angular head adapted to slidably fit said guide.

In testimony whereof I have hereunto afiixed my signature.

DENNIS F, LARKIN. 

